Fluid-Regulating Thermostat and Method of Manufacturing Such a Thermostat

ABSTRACT

This thermostat ( 1 ) comprises a body ( 10 ) which comprises a one-piece metal part ( 11 ) including simultaneously, in succession along the axis (X-X) of a thermostatic element ( 20 ) of the thermostat, a transverse tab ( 12 ) against which the piston ( 22 ) of this element can bear, a tubular part ( 13 ) centred on this axis and defining a shut-off seat ( 13 A), and two support arms ( 14 ) supporting a return spring ( 40 ) for returning this element, which arms extend lengthwise more or less in the axial direction of the element and each delimits, at their opposite end ( 14 A) to the tubular part, a surface ( 14 A 1 ) for contact with the spring against which surface the compressed spring is pressed. To make it easier to manufacture this body and to assemble it with the other components of the thermostat, each arm is, at its end ( 14 ) facing towards the tubular part, connected to the rest of the one-piece metal part in a way that can be deformed between a service position in which the contact surface is plumb with one end of the spring, and an assembly position in which this surface is away from the axis.

The present invention relates to a fluid regulator thermostat, inparticular for a cooling fluid of an internal combustion engine, andalso to a method of fabricating such a thermostat.

The invention relates more particularly to thermostats that combinefirstly a thermostatic element that is responsive to the temperature ofthe fluid to be regulated, controlling the shutting of a flow of fluidthrough the thermostat and associated with a return spring, and secondlya body within which there are arranged both said thermostatic elementand the spring. The body of the thermostat must satisfy conflictingconstraints: firstly the structure must be sufficiently rigid to absorbthe pressure of the fluid being regulated and the mechanical forcesassociated with operation of the thermostatic element and its returnspring, and secondly the structure must be sufficiently open to defineone or more paths for allowing the fluid to pass through the thermostat,and at satisfactory flow rates.

Traditionally, the body of this type of thermostat is molded out of aplastics material for numerous reasons, in particular ease and cost offabrication. Nevertheless, the use of a plastics material involvessignificant design constraints associated with the only moderatemechanical strength of the plastics material, in particular in terms ofresistance to creep: within a cooling circuit for an internal combustionengine, the body of the thermostat is subjected to vibration, and atcertain engine speeds, the temperature of the cooling fluid can reachvalues that are high. Taking these mechanical and thermal constraintsinto account requires the thermostat body, when made of plasticsmaterial, to be dimensioned with walls of significant thickness, therebylimiting the maximum flow rate possible through the thermostat.

To avoid that drawback in part, proposals have been made in the past toreinforce the structure of the plastics material body with one or moremetal pieces fitted thereto. In particular, a metal washer is sometimesprovided in the zone of the thermostat body that absorbs the reactionfrom the return spring of the thermostatic element. Nevertheless,recourse to fitting such metal pieces not only complicates the design ofthe thermostat body, thereby limiting options for installing thethermostat at various points within a cooling circuit and/or withindifferent circuits, but also complicates the fabrication of thethermostat since it requires a large number of parts to be assembled.

In the past, proposals have also been made to integrate the thermostatwithin a body made of two distinct parts of plastics material that areof generally tubular shape, and that are for fitting to each other withan interposed sealing gasket. That body forms a kind of housing thatpresents a major risk of leaking, and it generally incorporates aninternal reinforcing metal bracket for absorbing the forces associatedwith the work of the thermostatic element, thereby likewise complicatingthe design of the thermostat and its fabrication.

U.S. Pat. No. 3,351,279 and U.S. Pat. No. 3,792,813 propose using athermostat body that is made entirely out of metal, thereby ensuringgood mechanical strength. Nevertheless, such metal bodies raisefabrication problems and problems of assembly with the other componentsof the thermostat, in particular the thermostatic element and its returnspring.

Thus, U.S. Pat. No. 3,351,279 proposes a thermostat body in which one ofthe spring support arms is not formed integrally with the remainder ofthe body, but is fitted to the body either by means of a hinge or bywedging. Fabrication of the body is thus complex, and in operation theconnection zone between the fitted arm and the remainder of the bodypresents a risk of breaking or of malfunctioning.

U.S. Pat. No. 3,792,813 also envisages various metal embodiments forthermostat bodies, each made up of two distinct portions that are fittedtogether. In its FIG. 7, that document discloses a one-piece embodiment,in which two arms for supporting a spring of a thermostatic element aremade integrally out of the same material as the remainder of thethermostat body, which body can be made by stamping. Nevertheless,although U.S. Pat. No. 3,792,813 explains how the thermostat is to beassembled when the body is made of two parts, specifically by takingadvantage of its two-part structure for assembling the thermostaticelement and its spring in one of the parts of the body prior tofastening the other part thereto, that document is silent as to how toassemble the one-piece body with the other components of the thermostat.Thus, the one-piece solution proposed in U.S. Pat. No. 3,792,813 cannotbe made in practice, it being observed in addition that the arms of thethermostat body are inclined at 45° relative to the working axis of thethermostatic element and of its spring, such that, in operation, thosearms run the risk of splaying apart from each other under the action ofthe forces generated by the thermostatic element and the spring, therebyleading to malfunction of the thermostat.

The object of the present invention is to propose a thermostat, inparticular for a cooling circuit of an internal combustion engine, inwhich the body presents a structure that is effective in absorbing theforces associated with the work of the thermostatic element incorporatedin the thermostat, and that allows a substantial flow rate for theregulated fluid, while being easy to fabricate and assemble with theother components of the thermostat.

To this end, the invention provides a fluid regulator thermostat, inparticular for regulating a cooling fluid of an internal combustionengine, as defined in claim 1.

The fact of making the thermostat body of the invention as a one-piecemetal fitting presents firstly structural advantages that are inherentto the metal nature of the fitting: ability to withstand hightemperatures is improved, in particular in comparison with a body madeof plastics material, and the wall thickness of the body can be moderatewhile nevertheless achieving satisfactory mechanical strength, thisthickness being in particular less than the thickness of walls made ofplastics material and presenting a similar level of strength. Thestructure thus makes large fluid flow sections possible through thethermostat, and consequently allows high regulated flow rates. Inaddition, the one-piece metal body is easily obtained by working a metalsheet in appropriate manner, in particular by stamping.

In addition, the mechanical strength of the body, in particular relativeto the thermostatic element and its return spring, both during assemblyand during operation of the thermostat, makes it possible to avoidfitting stiffener pieces to the body, thereby facilitating design of thebody and also making it easy to implant at various different points in acooling circuit. The outside shape of the body can also be adapted atwill, e.g. so that the body can be put into place at the end of astainless steel tube prior to being covered by a hose, without it beingnecessary to interpose a sealing gasket, or for example so that theoutside shape of the body is close to that of a pre-existing thermostattube.

According to the invention, the deformable connection between thesupport arms and the remainder of the one-piece metal fitting of thethermostat body is provided to make it easier to fabricate thethermostat, enabling assembly to be performed quickly and easily withthe other components of the thermostat.

Other characteristics of this thermostat that are advantageous, taken inisolation or in any technically feasible combination, are set out inclaims 2 to 12.

The invention also provides a method of fabricating a fluid regulatorthermostat as defined above, which method is defined in claim 13, andpresents advantageous characteristics as defined in claim 14.

The invention can be better understood on reading the followingdescription given purely by way of example and made with reference tothe drawings, in which:

FIGS. 1 and 2 are longitudinal sections of a thermostat of the inventionon respective section planes are mutually perpendicular, the left-handhalves of these figures showing the thermostat while it is being putinto place within a fluid flow path, while the right-hand halves showthe thermostat once it has been put fully into place;

FIG. 3 is a perspective view of the body of the thermostat of FIGS. 1and 2, shown on its own, prior to being assembled with the othercomponents of the thermostat, the section planes of FIGS. 1 and 2 beingreferenced I and II respectively in FIG. 3;

FIG. 4 is a perspective view of the shutter member of the thermostat ofthe invention, shown on its own;

FIG. 5 is a fragmentary longitudinal section view of the thermostat ofFIGS. 1 and 2, on a section plane different from that of FIGS. 1 and 2,corresponding to the plane referenced V in FIG. 3; and

FIG. 6 is a section view analogous to FIG. 2 showing how the othercomponents of the thermostat are assembled in the body of FIG. 3, theleft and right halves of FIG. 6 being associated respectively withsuccessive steps in performing such assembly.

FIGS. 1 and 2 show a thermostat 1 for regulating the flow of a coolingfluid, e.g. flowing in a cooling circuit of an internal combustionengine. In operation, the thermostat is designed to be put into place ata connection zone between an outlet tube 2 from a heat exchanger formingpart of the cooling circuit and a hose 3 for conveying the liquid to adownstream point of the circuit. By way of example, the tube 2 is madeof metal, constituting the outlet from a heat exchanger associated witha system for exhaust gas recirculation (EGR). The EGR system is anantipollution device that injects some of the exhaust gas into theadmission tube of the engine in order to reduce combustion temperaturepeaks and thus reduce the formation of pollutants such as nitrogenoxides. As represented by arrow 4, the cooling fluid leaving the heatexchanger of the EGR system is admitted to the inlet of the thermostat 1that, as a function of the temperature of said fluid, controls whetherthe hose 3 is fed with the fluid, as represented by arrow 5. How thethermostat 1 is put into place in the junction zone between the tube 2and the hose 3 is described below.

For convenience, the description below is given relative to the flowdirection of the fluid through the thermostat 1 as shown in FIGS. 1 and2, with terms such as “up” and “top” designating a direction in the flowdirections 4 and 5, i.e. directed towards the top portions of FIGS. 1 to6, whereas terms such as “down” and “bottom” designate the oppositedirection. Thus, the cooling fluid sweeps vertically upwards through thethermostat 1 while it is open.

The thermostat 1 extends lengthwise in a vertical direction in FIGS. 1and 2 about a central axis X-X. It comprises four distinct componentsthat are assembled together in a manner that is described below,specifically an outer body 10, a thermostatic element 20, a shuttermember 30, and a spring 40.

The body 10, shown on its own in FIG. 3, is in the form of a one-piecemetal fitting 11 extending along and around the axis X-X, and withinwhich the other components 20, 30, and 40 are arranged.

The thermostatic element 20 comprises a bottom cup 21 centered on theaxis X-X and containing a thermally expandable material such as wax. Thecup is continuously immersed in the fluid feeding the thermostat 1 suchthat the element 20 is subjected to the temperature of the fluid. Theelement 20 also comprises a top piston 22 centered on the axis X-X andmovable relative to the cup 21 in translation along the axis X-X. Thispiston is movable under the effect of the thermally expandable materialcontained in the cup 21 expanding, the piston being deployed out fromthe cup when said material is heated. The piston 22 has a top endportion 22A that is stepped along the axis X-X: at its free end, thisportion 22A includes a top end peg 22A₁ integrally molded with the rod22A₂ constituting the remainder of the portion 22A and presenting adiameter smaller than that of the rod. A radial shoulder 22A₃ is thusdefined between the peg 22A₁ and the rod 22A₂.

In operation, the piston 22 is designed to be axially stationaryrelative to the body 10. For this purpose, the end portion 22A of thepiston bears axially against a wall 12A of the fitting 11, which wall iscentered on the axis X-X and generally occupies a plane that issubstantially perpendicular to said axis. The wall 12A is pierced by athrough cylindrical orifice 12A₁ on the axis X-X that presents across-section that substantially matches the cross-section of the topend peg 22A₁ of the piston 22.

The shutter member 30 comprises an annular main body 31 centered on theaxis X-X and permanently secured to the cup 21, e.g. being engaged as aforce-fit around a swollen portion 21A of the cup. At its top end, thebody 31 is provided with a peripheral rim 32 projecting radiallyoutwards from the body 31. This rim forms a member for closing off fluidflow through the thermostat 1. For this purpose, the rim 32 is adaptedto bear in leaktight manner against an associated seat constituted by awall 13A of the fitting 11, said wall being of frustoconical shapecentered on the axis X-X. In operation, since the piston 22 of theelement 20 is prevented from moving relative to the body 10, an increasein the temperature of the fluid feeding the thermostat causes the cup 21to move downwards in translation along the axis X-X, thereby moving theshutter member that is associated therewith, so that the rim 32 thenmoves away from the wall of the seat 13A so as to allow the fluid topass through the thermostat, towards the hose 3.

In order to guide the movement in translation of the cup 21 and of theshutter member 30 within the thermostat 1, the shutter member isadvantageously provided with four fingers 33 distributed uniformlyaround the outer periphery of the body 31. As shown in FIGS. 4 and 5,each finger 33 extends radially outwards from the outside face of thebody 31, beneath the rim 32, and beyond the rim 32. Each finger 33 isthus dimensioned in such a manner that the radial distance between theaxis X-X and the outer end face 33A of the finger is substantially equalto the radius of the inside face 13B₁ of the wall 13B of the fitting 11,which is cylindrical in shape on a circular base about the axis X-X. Asa result, when the cup 21 is driven in translation and entrains theshutter member 30 in corresponding manner, the end faces 33A of thefingers 33 slide against the inside face 13B₁ of the wall 13B, asrepresented by arrow 33B in FIG. 5. Since the fingers 33 are regularlydistributed around the outer periphery of the body 31, they areeffective in guiding the movement in translation of the shutter memberrelative to the cylindrical wall 13B, centering it on the axis of saidwall, i.e. on the axis X-X.

It can be understood that the inside diameter of the cylindrical wall13B is greater than the maximum outside diameter of the frustoconicalwall 13A. In practice, the wall 13A and the wall 13B situated axiallyimmediately beneath the wall 13A are made integrally out of the samematerial, being connected together via a radial shoulder 13C of thefitting 11. As a result, the walls 13A and 13B together with theshoulder 13C form a portion 13 of the fitting 11 that is tubular inshape with a solid peripheral wall, as can be seen clearly in FIG. 3.

As shown in FIGS. 1 to 3, the tubular portion 13 has its top endconnected to the wall 12A by two branches 12B that are diametricallyopposite about the axis X-X. Each branch 12B extends from a small regionof the top periphery of the wall 13A to the wall 12A in a generaldirection that slopes relative to the axis X-X. The wall 12A and the twobranches 12B thus form a tab 12 extending transversely relative to theaxis X-X and crossing said axis, with the fluid being free to flow oneither side thereof towards the hose 3.

At its bottom end, the tubular portion 13 is formed integrally with twoarms 14 of the fitting 11, which arms extend generally lengthwiseparallel to the axis X-X, being diametrically opposite each other aboutsaid axis, as can be seen in FIGS. 2 and 3.

The bottom end 14A of each arm 14 is in the form of a hook with itsrecess facing upwards. The recess is suitable for receiving the bottomend turn 41 of the spring 40, the hook shape ensuring that the turn 41is held in position transversely. In the assembled state of thethermostat 1, the spring 40 is interposed between the ends 14A of thearms 14 and the shutter member 30, with the top end turn 42 of thespring surrounding the cup 21. The spring 40 is designed to urge the cup21 towards the piston 22 when the thermally expandable materialcontained in the cup contracts, in particular during a drop in thetemperature of the fluid in which the cup is immersed. In practice, thespring 40 is assembled in the compressed state between the shuttermember 30 and the arms 14 so as to develop sufficient return force whilethe thermostat 1 is in operation. Under such conditions, it will beunderstood that the turn 41 presses downwards against the surface 14A₁at the bottom of the recess in the hook-shaped end 14A of each arm.

At its top end 14B, each arm 14 is made integrally with a small regionof the bottom periphery of the cylindrical wall 13B.

Thus, the one-piece metal fitting 11 constituting the body 10 includes,in succession along the axis X-X: the tab 12, the tubular portion 13,and the arms 14. This fitting 11 is advantageously obtained essentiallyby stamping a precut metal sheet, the tab 11 and the arms 14 being maderespectively by stamping together with the tubular portion 13. To makethis metal sheet easier to stamp, the arms 14 are angularly offset byabout 90° around the axis X-X from the branches 12B of the tab 12, whichamounts to saying that the angle a formed between the planes I and IIreferenced in FIG. 3 is about 90°.

The orifice 12A₁ is easily obtained by cutting or punching out from thewall 12A, in other words by an operation that is inexpensive and easy toautomate.

The thermostat 1 is assembled by arranging, within the fitting 11,simultaneously the thermostatic element 20 with the cup 21 thereofpreviously being provided in stationary manner with the shutter member30, and the compressed spring 40. To make assembly easier, the top end14B of each arm 14 is advantageously deformable in the manner of a hingeso that each arm can be moved relative to the remainder of the fitting11 by being tilted about an axis 14B₁ that extends level with the end14B in a direction that is substantially circumferential about the axisX-X, as shown in FIG. 6. More precisely, if the fitting 11 is consideredat the end of its own fabrication by stamping, the arms 14 do not extendaccurately parallel to the axis X-X, but are inclined relative to saidaxis, sloping downwards away from the axis, as shown in FIG. 3 and inthe left-hand portion of FIG. 6. In longitudinal section as in FIG. 6,the angle δ formed between the longitudinal direction of each arm andthe axis X-X is a few degrees, e.g. about 5° . In other words, theradial distance d_(14A) in the left-hand portion of FIG. 6 between theend 14A of each arm and the axis X-X is greater than the radial distancebetween the end 14B and the axis.

In this position, each of the ends 14A is far enough away from the axisX-X not to impede axial insertion from below of the other components ofthe thermostat 1 into the body 10. In other words, the above-mentionedradial distance d_(14A) is designed to be greater than the correspondingradial distances d₃₀ and d₄₁ of the shutter member 30 carried by thethermostatic element 20 and of the spring 40, as shown in the left-handportion of FIG. 6.

The thermostatic element 20 is then inserted between the arms 14 andthen into the inside of the tubular portion 13, as represented by arrowA, until the top end peg 22A₁ of the piston 22 is received in thethrough orifice 12A₁ in the wall 12A, thus enabling the element 20 to becentered inside the fitting 11 on the axis X-X. Inserting thethermostatic element as centered in this way continues until theshoulder 22A₃ comes to bear axially against the bottom structure 12A₂ ofthe wall 12A, as in the right-hand portion of FIG. 6. The peg 22A₁ isthen clearly visible from the top of the thermostat, inside the orifice12A₁, thus making it possible to verify visually that the element 20 hasbeen put into place properly, even if only a top end portion of the body10 can be observed freely.

Since the shutter member 30 has previously been fitted in stationarymanner around the cup 21, inserting the thermostatic element 20 enablesthe shutter member 30 to be put into place inside the tubular portion13, with the fingers 33 bearing slidably against the inside face 13B₁ ofthe wall 13B. To prevent the top ends 14B of the arms 14 impeding thepositioning of these fingers 33 inside the wall 13B, the angularpositioning about the axis X-X between the shutter member 30 and thefitting 11 is advantageously designed so that each finger 33 is offsetby about 45° relative to the arm 14 around the periphery of the wall13B, which amounts to saying that the angle β formed between the lanesmarked II and V in FIG. 3 is substantially to 45°.

After the thermostatic element 20 has been inserted in the fitting 11,the spring 40 is inserted axially upwards between the arms 14, i.e.following the same insertion direction A as the element 20. In avariant, the spring could be inserted simultaneously with thethermostatic element. Once the turn 42 bears against the shutter member30, the upward insertion movement is continued so as to compress thespring against the shutter member until the turn 41 lies axially abovethe axial level of the bottom ends 14A of the arms 14, as shown in theright-hand portion of FIG. 6. In practice, the spring can be compressedby means of tooling that extends across the axis X-X between the arms 14along the periphery of the fitting 11. While maintaining the spring inthis compressed state, the arms 14 are then tilted inwards, i.e. towardsthe axis X-X about their respective axes 14B₁, as represented by arrowF₁₄ in the right-hand portion of FIG. 6. Each of the ends 14A of thearms thus comes closer to the axis X-X until these ends lie axiallyunder the turn 41. The arms then extend substantially parallel to theaxis X-X, thus enabling the arms to withstand effectively the forcesdelivered by the spring and also the forces generated in operation bythe thermostatic element. The tooling that is holding the spring 40 inthe compressed state is then withdrawn, thus enabling the spring torelax partially, until its turn 41 comes to bear against the bottomfaces 14A₁ at the ends 14A of the arms 14. The turn 41 is held in therecesses defined by the hook shape at the ends 14A, thereby preventingthese ends from moving apart were the ends 14B to tend to deformspontaneously so as to bring the arms 14 back into their initial slopingconfiguration as they were at the end of stamping. The thermostat isthen in its assembled configuration of FIGS. 1 and 2 and is thus similarto a one-piece cartridge, ready for subsequently being implanted withina fluid circuit.

The thermostat 1 is particularly quick and easy to assemble, since bothof the essential steps of such assembly, namely inserting thethermostatic element 20 and the spring 40 following the linear movementA, and tilting the arms about the axes 14B₁ following the movement F₁₄,can be automated easily, particularly on an assembly line. Furthermore,no part, and in particular no stiffener part, needs to be fitted to thefitting 11 having the element 20 and the spring 40 engaged therein.

The thermostat 1 can subsequently be put into place in the connectionregion between the tube 2 and the hose 3. For this purpose, and as shownin the left-hand portions of FIGS. 1 and 2, the body 10 and the tube 2are brought axially towards each other along arrow B so that the arms 14are inserted in full into the inside of the tube 2. Advantageously, thediameter of the wall 13B is designed to be substantially equal to theend diameter of the tube 2, while the radial distance between theoutside faces of the arms 14 is designed to be smaller than the insidediameter of said end of the tube 2, a small radial shoulder thusconnecting each top end 14B of each of the arms with two smalldiametrically-opposite regions of the bottom end of the wall 13B. As aresult, putting the thermostat 1 into place at the end of the tube 2consists in inserting the arms 14 into said end of the tube until thebottom end face 13B₂ of the wall 13B where it is free between the arms14 comes to bear axially again the top end face 2A of the tube 2, as canbe seen in the plane of FIG. 1.

In order to enable the thermostat 1 to be held at the end of the tube 2,in particular prior to the hose 3 being put into place, each arm 14 isprovided in its main portion with a tongue 15 formed integrally with theremainder of the arm. By way of example, each tongue is obtained byappropriately cutting the wall constituting the arm 14 and then curvingthe tongue as cut out in this way about an axis 15B₁ that iscircumferential about the axis X-X. Each tongue 15 then has a bottom end15B integral with the main portion of the arm 14 where the axis 15B₁extends, and a free top end 15A, with the body of the tongueinterconnecting the ends 15A and 15B presenting in longitudinal sectiona profile that is curved with its concave side facing downwards. Atrest, i.e. prior to the thermostat 1 being put into place in the end ofthe tube 2, the end 15A of each tongue extends beyond the outer envelopesurface of the arm 14 away from the axis X-X.

When the body 10 and the tube 2 are moved towards each other along arrowB, the end face 2A of the tube comes to bear against the concave outsidesurface of each tongue and slides against said surface causing thetongues to tilt inwards, towards the axis X-X, about the respective axes15B₁, as represented by arrow 15B₂ in the left-hand portion of FIG. 2.When the end face 2A subsequently comes to bear against the end face13B₂ of the wall 13B, each of the tongues 15 tilts elastically in theopposite direction to return towards its initial position, because ofthe presence of a hole 2B passing radially through the top end wall ofthe tube 2, as represented by arrow 15B₃ in the right-hand portion ofFIG. 2. In other words, each tongue 15 engages the associated orifice 2Bin the tube 2, thereby preventing untimely separation of the thermostat1 from the tube. It is still possible to separate the thermostat fromthe tube, by causing both tongues 15 to tilt simultaneously inwards,with this being done by using suitable tools having tips that can beinserted from the outside into each of the orifices 2B.

The hose 3 is subsequently fitted around the top end of the tube 2, asrepresented by arrow C in FIGS. 1 and 2. The bottom end of the hosecovers the thermostat 1 and the top end of the tube 2 so as to extendaxially over an outer peripheral bead 2C on the tube 2, as shown in theright-hand portion of FIGS. 1 and 2. The hose 3 is held more securely inplace around the tube 2 by means of a peripheral collar 6 or the like.

Various arrangements and variants of the thermostat 1 and of its methodof fabrication can also be envisaged, including the following examples:

-   -   more than two support arms 14 may be formed integrally with the        remainder of the fitting 11, in particular arms that are        distributed uniformly around the axis X-X;    -   the retaining tongues 15 may be incorporated within the body 10        in locations other than in a main portion of each arm 14, in        particular depending on the shape of the tube 2 into the end of        which the thermostat is to be placed;    -   the outside shape of the body 10 is not restricted to that shown        in the figures; in particular, the region of the body 10 that        extends axially between the wall of the seat 13A and the bearing        wall 12A of the thermostatic element 20 may include a tubular        wall centered around the axis X-X so as to give this zone of the        fitting 11 a tubular shape as presently exists with standard        thermostats, in particular including a peripheral fold obtained        by stamping together with the remainder of said additional        tubular wall, where there is preferably fitted a sealing gasket        for engaging the end of the hose or a similar tube fitted onto        the thermostat;    -   the presence of the shutter member 30 fitted around the cup 21        is not essential, if provision is made for the swollen portions        21A of the cup to act directly as a member for closing the        shutter seat defined by the wall 13A; this applies for example        when a small amount of liquid leakage through the “closed”        thermostat can be tolerated, in which case contact between the        metal cup 21 and the wall of the seat 13A need not be completely        leaktight; and/or    -   to avoid the arms 14 tending to return to their initial inclined        configuration once they have been moved towards each other to        support the compressed spring 40, a variant of the fabrication        method consists in obtaining the fitting 11, at the end of the        stamping operation, with its arms in a geometrical configuration        that is substantially identical to their configuration in        operation, i.e. with the arms substantially parallel to the axis        X-X; under such circumstances, prior to inserting the element 20        and the spring 40 into the inside of the fitting 11, it is        necessary to splay the arms apart radially away from the axis        X-X, by deforming their ends 14B so as to cause the arms to tilt        outwards about the axes 14B₁, until the radial distance d_(14A)        is greater than the radial dimensions d₃₀ and d₄₁ of the        components of the thermostat that are to be inserted between the        arms.

1. A thermostat for regulating a fluid, in particular a cooling fluid ofan internal combustion engine, the thermostat comprising: a thermostaticelement that comprises firstly a cup filled with a thermally expandablematerial and adapted to shut a fluid flow through the thermostat bycoming into contact against an associated seat, and secondly a pistonmovable relative to the cup along an axis (X-X) of the element under theeffect of the thermally expandable material during a variation in thetemperature of the fluid to be regulated; a compressed spring adapted tourge the cup and the piston towards each other; and a fluid flow bodyfor passing the fluid flow to be regulated, the body having arrangedtherein the thermostatic element and the spring in such a manner that,in operation, the piston is held stationary relative to the body, theshutter seat associated with the cup is connected in fixed manner to thebody, and the decompression force of the spring is absorbed by the body,the body comprising a one-piece metal fitting (11) which includes insuccession along the axis of the thermostatic element: a tab againstwhich the piston bears in stationary manner and extending along adirection that is transverse relative to the axis of the element; atubular portion that is substantially centered on the axis of theelement and that defines the shutter seat; and two spring support armsthat extend lengthwise generally in the axial direction of the element,each defining at a first one of its ends remote from the tubularportion, a contact surface for the spring, against which the compressedspring is pressed; wherein each arm is, at its second end directedtowards the tubular portion, each arm is connected to the remainder ofthe one-piece metal fitting in deformable manner between an operatingposition in which the contact surface is disposed in register with oneend of the spring in the decompression direction of the spring, and anassembly position in which the contact surface is spaced apart from theposition it occupies when the arm is in its operating position, goingaway from the axis (X-X) of the thermostatic element.
 2. A thermostataccording to claim 1, wherein each arm is movable between its assemblyand operating positions by tilting about an axis that is substantiallycircumferential about the axis (X-X) of the thermostatic element.
 3. Athermostat according to claim 1 wherein, in the operating position, thearms extend substantially parallel to the axis (X-X) of the thermostaticelement.
 4. A thermostat according to claim 1, wherein the first end ofeach arm presents a hook shape with its recess adapted to receive an endturn of the spring, the bottom of said recess defining the contactsurface.
 5. A thermostat according to claim 1, wherein the two arms arediametrically opposite about the axis (X-X) of the thermostatic element.6. A thermostat according to claim 5, wherein the two arms are offsetangularly about the axis (X-X) of the thermostatic element by about 90°relative to two branches forming portions of the bearing tab anddiametrically opposite about said axis.
 7. A thermostat according toclaim 1, wherein the end portion of the piston remote from the cup isstepped along the axis (X-X) of the thermostatic element in such amanner that the free end of the piston presents a maximum transversedimension that is less than the transverse dimension of the remainder ofsaid end portion, a shoulder being formed between said free end and theremainder of said end portion, and in that the bearing tab includes abearing surface for said shoulder and a receiver orifice for receivingsaid free end, said orifice passing axially through a corresponding wallof the tab and opening out into the bearing surface.
 8. A thermostataccording to claim 7, wherein the receiver orifice and the free end ofthe piston present cross-sections that are substantially complementaryto each other.
 9. A thermostat according to claim 1, wherein saidthermostat further includes a shutter member fitted in stationary mannerto the cup, adapted to come into leaktight contact against the seat toclose the flow of fluid through the thermostat (1), and provided withmeans for sliding against the inside face of a wall of the tubularportion, that is distinct from the shutter seat.
 10. A thermostataccording to claim 9, wherein the slider means comprise a plurality ofdistinct fingers distributed in substantially uniform manner around theperiphery of the shutter member.
 11. A thermostat according to claim 1,wherein the one-piece metal fitting further includes at least onedeformable tongue adapted to engage elastically an orifice or anassociated swelling of a tube when said fitting is inserted at least inpart into said tube.
 12. A thermostat according to claim 11, the leastone tongue is integral with the or one of the arms.
 13. A method offabricating a fluid regulation thermostat according to claim 1, in whichmethod the one-piece metal fitting is obtained by stamping a metal sheetin such a manner that the bearing tab, the tubular portion, and the armsare formed as a single piece by stamping, the method being characterizedin that it comprises the following successive steps: inserting thethermostatic element and the spring along the axis (X-X) of thethermostatic element into the inside of at least the tubular portion;compressing the spring axially towards the tubular portion beyond theaxial position of the first end of each arm; while keeping the springcompressed in this way, moving the first end of each arm towards theaxis (X-X), by deforming the opposite end (14B) of the arm, until thecontact surface is disposed substantially axially in register with thespring; and decompressing the spring until it comes to press axiallyagainst the contact surface of each arm.
 14. A method according to claim13, wherein, while being stamped, the one-piece metal fitting isobtained directly with the first end of each arm at a radial distancefrom the axis (X-X) of the thermostatic element that is greater than thecorresponding radial dimensions of said element and of the spring.